Financial Guarantees in Force - Summary of Financial Guarantee Portfolio Diversification by Type of Guaranteed Bond (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	$ 22,613	$ 28,020
Public Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	10,547	12,360
Public Finance [Member] | Lease and Tax-backed Revenue [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,979	3,196
Public Finance [Member] | General Obligation [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,301	1,612
Public Finance [Member] | Housing Revenue [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	5,491	5,610
Public Finance [Member] | Other [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,776	1,942
Structured Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	3,612	4,904
Structured Finance [Member] | Mortgage-backed and Home Equity [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,930	2,724
Structured Finance [Member] | Investor-owned Utilities [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,103	1,556
Structured Finance [Member] | Other Structured Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	579	624
International Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	8,454	10,756
International Finance [Member] | Asset Backed and Other [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,083	1,276
International Finance [Member] | Investor-owned and Public Utilities [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	2,583	3,283
International Finance [Member] | Sovereign/Sub-sovereign [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	4,077	5,141
International Finance [Member] | Transportation [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	$ 711	$ 1,056